The present invention relates to a method for preheating a laminate structure in which a plurality of polymer plates and conductive metal plates are laminated alternately, and a method and apparatus for manufacturing a laminated body.
Such laminated bodies include, for instance, a laminated rubber body and are variously used for antiseismic or quake-absorbing apparatus and the like.
The laminated rubber body is manufactured by alternately laminating steel plates and raw rubber plates within a mold, and, during heating the mold, pressure is applied by a press machine.
However, since a raw rubber plate as a constituent of the laminated rubber body has a small thermal conductivity, there is a big difference in rising speed of temperature between a portion of the plate close to a heat source and another portion remote therefrom. This causes an uneven cure of raw rubber plates and thereby results in uniformless adherence between raw rubber plates and steel plates and unevenness in substantial characteristics of the resultant laminated rubber body. While it is possible to secure a certain degree of substantial characteristics by gently raising the temperature of the sold, the molding time would be greatly prolonged. In this respect, in order to reduce the time for pressure molding and stabilize substantial characteristics, there have been recently employed the following methods (1) (2) wherein raw rubber plates and steel plates are heated in advance up to a temperature not to cause any trouble in their substantial characteristics and workability before cure-adhesion thereof. However, each still has drawbacks.
(1) Method 1
In this method, layers made of a raw rubber plate and a steel plate to be laminated are respectively preheated.
Referring to FIG. 4, in this method, each layer made of a raw rubber plate 1 and a steel plate 2xe2x80x2 is placed on each of a plurality of shelves t within a drying oven Kxe2x80x2, and heated up respectively by hot blast (shown by rightward arrows).
In this method, after preheating, the layers of the raw rubber and steel plates 1, 2xe2x80x2 need to be laid and combined together in the mold for subsequent pressure molding. However, since a rise in temperature makes the raw rubber plates 1 soft and this makes laying work difficult, the practical preheating temperature will be limited. As a result, an initial curing temperature cannot be high, and reducing the curing time will not be effectively achieved.
(2) Method 2
In this method, a plurality of raw rubber plates and steel plates are alternately disposed and then preheated as one combined body.
Referring to FIG. 5, in this method, using a center core A1xe2x80x2 and an outer frame A2xe2x80x2 arranged within a drying oven Kxe2x80x2, a plurality of raw rubber plates 1 and steel plates 2xe2x80x2 are disposed alternately and then heated as one body by hot blast (shown by rightward arrows).
In this method, since superposing layers after preheating can be eliminated, the preheating temperature can be raised relatively high. However, this method employs a heating system from outside by hot blast, rise in temperature of an inner layer is delayed compared with that of an outer layer. This is apparent from FIG. 2, after 120 minutes from the start of heating, the outside rubber reaches a preheating limit temperature of 80xc2x0 C., but the temperature of the inside rubber only rises up to approximately 60xc2x0 C. Therefore, in order to obtain a substantially uniform temperature distribution of the laminate structure, heating must be performed gently, not rapidly, and this prolongs the preheating time. As a result, the time for pressure molding will not be effectively reduced.
The data of FIG. 2 were obtained under the following conditions.
Raw Rubber Plate 1
diameter: 520 ma, thickness: 6 mm, hole diameter: 90 mm Steel plate 2xe2x80x2
diameter: 500 mm, thickness: 3 mm, hole diameter: 90 mm Flange
diameter 500 mm, thickness: 25 mm, hole diameter: 90 mm Temperature of hot blast
80xc2x0 C.
Instead of raw rubber plates, polymer plates may be used in laminated bodies utilized for various purposes other than for antiseismic or quake-absorbing apparatus. Such polymer plates may also be required in some instances to be heated up to a desired temperature with a uniform temperature distribution and in a short time.
Next, the combined rubber body is further processed by (1) heating it up to a rubber fluidizing temperature (80-95xc2x0 C.) and pressing it to form an integrated laminated rubber body, and (2) securing its desired product dimensions by suppressing thermal vertical expansion of the laminated rubber body and, under a constant pressed condition, curing the rubber and cure-adhering the steel and rubber plates (a cure-adhesion temperature 110-125xc2x0 C.). However, since the raw rubber plates as constituent of the laminated rubber body have a small thermal conductivity, there is a large difference in temperature rising speed between a portion of the rubber close to a heat source and another portion remote therefrom. This causes uneven curing and thereby results in unevenness in substantial characteristics of the laminated rubber body (vertical elastic modulus, shear modulus, adhesion between raw rubber plates and steel plates, etc.).
Various methods have been tried to overcome these problems but temperature difference between inside and outside portions could not be eliminated. As a result, in order to avoid bad influence to products, the molding time must be prolonged. Further, measures for improvement requires a number of processes and an innovative method has not been found yet.
In case of adhesion of other type of laminated structures such as with synthetic resin plates or ceramics plates and conductive metal plates, there may be also a problem due to the temperature difference between inside and outside portions.
In is an object of the present invention to provide a method for preheating a laminate structure in which polymer plates incorporated in the structure are heated up to a desired temperature with a substantially uniform temperature distribution and in a short time. It is another object of the present invention to provide a method and apparatus for manufacturing a laminated body with which a laminate structure is heated up to a specific temperature range with few temperature difference between an inner and an outer portion thereof and in a short time.
In order to achieve the above objects, the present invention includes the following means.
According to a first embodiment of the present invention, there is provided a method for preheating a laminate structure which includes applying through electrodes a high-frequency voltage in a lamination direction of the laminate structure having alternate lamination with a plurality of polymer plates and conductive metal plates, so as to dielectrically heat said polymer plates.
According to a preferred embodiment of the present invention, in the above method for preheating a laminate structure, the plurality of conductive metal plates are parallel with each other.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, intervals between any adjacent conductive metal plates are substantially the same.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, the high-frequency voltage is applied between the electrodes disposed on opposite ends of the laminate structure in the lamination direction.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, the outermost opposite conductive metal plates of the laminate structure function as the electrodes.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, flanges made of conductive metal plate are provided on outer faces of the outermost opposite plates of the laminate structure and function as the electrodes.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, conductive metal plates are provided in a manner of contacting with outer faces of the outermost opposite plates of the laminate structure and function as the electrodes.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, the electrodes are heated by heating means.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, the laminate structure has a through bore in the lamination direction and a core member made of non-conductive material is inserted into the through hole so as to position the plurality of polymer and conductive metal plates.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, an annular housing member surrounds the laminate structure in contact with the peripheral lamination surface thereof so as to position the plurality of polymer and conductive metal plates.
According a preferred embodiment of the present invention, in the above method for preheating a laminate structure, at least one of the housing member and the core member has a coefficient of dielectric loss not higher than 0.3.
According to a further embodiment of the present invention, there is provided a method for manufacturing a laminated body which includes accommodating an alternate laminate structure with a plurality of polymer plates and conductive metal plates in an annular housing member which is made of nonconductive material and surrounds the laminate structure in contact with the peripheral lamination surface thereof, applying through electrodes a high-frequency voltage to the laminate structure in a lamination direction so as to dielectrically heat the polymer plates, and applying pressure to the laminate structure in the lamination direction by a pressing means at least after completion of the high-frequency voltage applying process.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, the plurality of conductive metal plates are parallel to each other.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, intervals between any adjacent metal plates are substantially the same.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, heating by heating means is also provided under the process of applying the high-frequency voltage.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, polarity of the high-frequency voltage is reversed every fixed time.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, the high-frequency voltage is applied between the electrodes provided on opposite ends of the laminate structure in the lamination direction.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, the electrodes are the outermost opposite conductive metal plates of the laminate structure.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, the electrodes are flanges made of conductive metal plates and provided on the opposite outermost sides of the laminate structure.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, the electrodes are conductive metal plates provided in a manner of contacting with the outer faces of the outermost opposite plates of the laminate structure.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, the electrodes are pressing plates made of conductive metal plate as the pressing means.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, the electrodes are heated by heating means.
According a preferred embodiment of the present invention, in the above method for manufacturing a laminated body, the dielectric heating is conducted in a manner such that a central core made of non-conductive material is inserted in a through bore of the laminate structure extending in the lamination direction.
According to another embodiment of the present invention, there is provided an apparatus for manufacturing a laminated body which is for heat integrating an alternate laminate structure with a plurality of polymer plates and conductive metal plates, and includes an annular housing member which is made of non-conductive material and surrounds the laminate structure in contact with the peripheral lamination surface thereof, dielectric heating means for dielectrically heating the polymer plates by applying a high-frequency voltage in a lamination direction of the laminate structure through electrodes, and pressing means to press the laminate structure in the lamination direction.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, the pressing means gives pressure at least after completion of a high-frequency voltage applying process.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, the dielectric heating means has switching means for reversing polarity of the high-frequency voltage every fixed time.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, electrodes receiving the high-frequency voltage are provided at opposite ends of the laminate structure in the lamination direction.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, the outermost opposite conductive metal plates of the laminate structure function as the electrodes, and the dielectric heating means is capable of applying the high-frequency voltage between these outermost opposite conductive metal plates.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, flanges made of conductive metal plates and provided on the outermost opposite sides of the laminate structure function as the electrodes, and the dielectric heating means is capable of applying the high-frequency voltage between these flanges.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, conductive metal plates provided in a manner of contacting with the outer faces of the outermost opposite plates of the laminate structure function as the electrodes, and the dielectric heating means is capable of applying the high-frequency voltage between the conductive metal plates.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, the pressing means includes a pressing plate made of conductive metal material and applies pressure to the laminate structure during the dielectric heating, and the dielectric heating means is capable of applying the high-frequency voltage between these pressing plates.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, the electrodes are provided with heating means.
According a preferred embodiment of the present invention, the above apparatus for manufacturing a laminated body further includes a non-conductive positioning means for positioning the plurality of polymer and conductive metal plates to be laminated, the positioning means includes a core member to be inserted in a through bore provided in the laminate structure and extending in the lamination direction.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, at least one of the housing member and the core member has a coefficient of dielectric loss not higher than 0.3.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, the housing member is a split-mold.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, the positioning means supports the peripheral lamination surface of the laminate structure.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, the laminate structure has a through bore extending in the lamination direction and the positioning means supports an inner peripheral surface of the laminate structure which defines the through bore.
According a preferred embodiment of the present invention, in the above apparatus for manufacturing a laminated body, the positioning means has a coefficient of dielectric loss not higher than 0.3.